Manufacture of polypentaerythritols



' as Patent No, 2,401,749.

Patented May 18, 1948 2,441,597

UNITED STATES PATENT OFFICE MANUFACTURE OF POLYPENTAERYTH- RITOLS JohnP. Remensnyder, Metuclien, N. 1., Philip I. Bowman, Syracuse 10, N. Y..and Robert H. Barth, Rldzewood. N. J., assiznors to Heyden ChemicalCorporation, New York, N. Y., a corporatlon of Delaware No Drawing.Application April 24, 1943, Serial No. 484,478

7 1 9 Claims. (01. 260-615) 2 This invention relates to an improvedprocess termed pleopentaerythritol." According to the for themanufacture of pentaerythritol and best evidence .available,pleopentaerythritol is polypentaerythritols by the action ofacetaldeprobably a mixture of dipentaerythritol, trihyde andformaldehyde in the presence of an pentaerythritol, and possiblyadditional related alkali. The invention relates to a process simpalcohols. ilar to that described in application Serial No. The materialreferred to as pleopentaerythri- 442,620, filed May 12, 1942,- byRaymond F. tol was crystallized from 100 times its weight'of Burghardtand Robert H. Barth, which has issued water. The product obtained is acrude tripentaerythrltol. If this is recrystallized twice from It iswell known that pentaerythritol and 10 water, a pure tripentaerythritolis obtained, polypentaerythritols are formed by the reaction which has amelting p int of 242-248" 0.. an he of 4 to 5- molecules of formaldehydewith 1 following analysis: molecule of acetaldehyde in the presence of 1to 1 equivalents of alkali. Alkalies which have Percent Percent beensuggested are the hydroxides of sodium, calll cllmlmd Fmmd cium,potassium and barium, as well as certain carbonates such as those ofsodium and potas- 3g &3; slum. In commercial practice the alkalies mostcommonly used are sodium hydroxide and ca cium hydroxide, althoughsodium hydroxide has a The fmfmula be as not been used generaly, sinceit has been con- 0310K CHIOH 03:03

sidered too strong a condensing agent. HocHFc-cm-o-cm-c-cnr-o-cm--cn,o11

In the manufacture of pentaerythritol by the H'OH H203 condensation ofacetaldehyde and formaldehyde, there are also formed smaller amounts ofother 15 This compound reacts with formaldehyde in hydroxylatedsubstances. One of these, which the presence of aqueous hydmchlorlc acidto give is obtained in a considerable amount, is dipencompmmd' meltingPoint 176478, which taemhmol, which is an ether having the correspondsto the following formula and has the lowing structure: followinganalysis:

. on on on 3 3 HOHzC- -CH:O-OHa- OH:OH J, (I: A 4! 2 H2011 H103 g H! E:H: is: H,

helm Greven, Krefeld, 1930). Another hydroxy- 38 lated substance, whichis obtained in somewhat Per cent Percent smaller amounts, is white andcrystalline, melts mm at 230-240 C., and has a hydroxyl value of 33%.

The chemical structure of s substance is notSt'i'iitea::I::1:1::::::::::::::::::::::::: $133 153 known, and there isa possibility that it is a mix- 40 Molecular welsht 408.4 413 ture ofchemical entities. It seems fairly certain,

however, that it is related to dipentaerythritol in Whentripentaerythritol is acetylated with that it contains pentaerythritolresidues bound acetic anhydride a compound is obtained having by etherlinkages. Regardless of chemical struca melting point of 85 0., andwhich corresponds ture, for purposes of definition in this speciflcatothe following formula. and has the following tion and in the claims,this substance will be analysis:

Dipentaerythritol, tripentaerythritol. and Plecpentaerythrltol may begrouped together under the generic term polypentaerythritols, by whichterm is meant those compounds, having higher molecular weights thanpentaerythritol which are formed either actually or theoretically byetherifying one or more of the hydroxyl groups of pentaerythritol withother pentaerythritol residues.

The processes heretofore known for the production of pentaerythritol andpolypentaerythritols have always involved the use of dilute alkali and adilute solution of the two aldehydes. The total concentration ofaldehydes has always been less than 20%, usually to This has been doneapparently to avoid side reactions which give syrupy, dark coloredproducts. The reaction temperatures which are reported are within therange from to 50 C.

In the copending application Serial No. 442,620 (Patent No. 2,401,749)are described conditions which increase the yield of solid products,namely pentaerythritol and polypentaerythritols. These conditionsinclude a lowered reaction temperature and a higher concentration ofaldehydes. In the process described in the said copending applicationspecial attention was paid to the formation of a high yield of fairlypure pentaerythritol containing a minimum of polypentaerythritols,including about 54.0% dipentaerythritol, This mixture represented about85-90% of the total products, and the polypentaerythritols accountedfor. 10-15% when separated in the manner described in the examples.

The main purpose of this invention is toincrease the ratio ofpolypentaerythritols to the pentaerythritol. These polypentaerythritolsare very useful in the resin and coating industries. This increase inthe proportion of polypentaerythritol is efiected not by changing theconditions which were found to be so beneficial in the said ccpendingapplication, but by incorporating those conditions with a newlydiscovered fact. This fact is that the proportion ofpolypentaerythritols is increased if pentaerythritol in some form isadded to the reaction medium. The pentaerythritol may be added from apreviously prepared batch, and may serve as a, reactant for theformation of polypentaerythritols. If, however, the conditions of thesaid copending application are not used, namely, that the temperaturesduring the addition of the acetaldehyde be between 15 and 30 0.,preferably between 20 and C., and the concentration of the formaldehydesolution used be 20-30%, and of the acetaldehyde be 100%, poor totalyields of pentaerythritol and is not necessary to use purepentaerythritol, and both crude wet material from commercial evaporators(which may contain a high ash of sodium formate) or a high qualityreaction liquor of the type obtained from the process described in thesaid copending application, or a mixture, may be utilized. I

It has been further discovered that by use of proportions of sodiumhydroxide in excess of 1.4 mole per mol of acetaldehyde, preferably 1.7to 2 mols, it is possible to increase the proportion oftrlpentaerythritol produced. The use of stronger formaldehyde solutions,up to a concentration of formaldehyde, and the use of highertemperatures, up to 40 C., in completely enclosed reactors is desirablefor the purpose of increasing the ratio of polypentaerythritols tomonopentaerythritol and in maintaining high yields of con densationproducts.

The following examples illustrate our invention:

Example 1.To a mixture consisting of 1500 parts of 20% formaldehydesolution (approximately 10 mols) containing 2'12 parts ofmonopentaerythritol (approximately 2 mols) and 362 parts of 31% sodiumhydroxide solution (approximately 2.8 mols) were added slowly 88 partsof acetaldehyde (approximately 2 mols). The time of addition of theacetaldehyde was 1 hour. The temperature maintained during the additionof the acetaldehyde was 22 C. The mixture was then kept at a temperatureof 58 C. for 2 hours,

\ after which time the formaldehyde concentration determined bytitration with sodium bisulflte solution corresponded to 0.32%formaldehyde. The mixture was neutralized to a pH of 8 with formic acid.and the specific gravity was adjusted to 1.100 at 25/25 C. Thepieopentaerythritol was filtered ofi. washed and dried. The filtrate wasconcentrated to a specific gravity of 1.270 at 25 G. under vacuum. andthe crystals of technical pentaerythritol filtered, washed well withmethanol, and dried.

The pieopentaerythritol was found to contain 35.4% tripentaerythritol,25% dipentaerythritol, and 37.6% of monopentaerythritol by fractionalcrystallization. Upon analysis, the fraction of technicalpentaerythritol obtained from the filtrate was found to contain 96.8%monopentaerythritol and 3.2% dipentaerythritol, by fractionalcrystallization.

The total yield of tripentaerythritol based on the acetaldehyde addedwas 11.85%; that of dipentaerythritol was 12.8%; and that ofmonopentaerythritol was 51.5%. The total yield of solids was 76.15%,based on the acetaldehyde, the weight of monopentaerythritol having beencorrected for the monopentaerythritol added at the start.

Example 2.To a mixture consisting of 1500 parts of 20% formaldehydesolution (approximately 10 mols), 272 parts of technical pentaerythritoi(approximately 2 mols). and 362 parts of 31% sodium hydroxide solution(approximatedipentaerythritol are obtained, although the ratio r ly 2.8mols) were added slowly 88 parts of acetaldehyde (approximately 2 mols).The time of addition of the acetaldehyde was 1 hour. The temperaturemaintained during the addition of the acetaldehyde was 22 C. The mixturewas kept at a temperature of 58 C. for 2 hours, after which time theformaldehyde concentration determined by titration with sodium'bisulfltesolution corresponded to 0.05%. neutralized to a pH of 8 with formicacid, and the smcific gravity was adjusted to 1.100 at 25 not by aproper choice of ratios of reactants. It to he plecpenta y ri was l dfi,

Th mixture was I washed an ddl 'ldd i filtrate was concentrated Y Thepleopentaerythritoi was found to contain 44.4% tripentaerythritol, 34%dipentaerythritol,

and 21.6% monopentaerythritoi by fractional crystallization.- Uponanalysis the fraction of technical pentaerythr'itol obtained from thefiltrate was found to contain 90% monopentaerythritol anddipentaerythritol by fractional crystallization.

The yield of tripentaerythritol based on the acetaldehyde added was9.65%; that of dipentaerythritol was 23.2%; and thatofmonopentaerythritol was 47.8%. The total yield of solids was80.85%,based on the acetaldehyde.

This example, which describes a procedure substantially identical withthe procedure of Example 1, iliustratesthe possible variations, inyields, which may be expected in the practice of the process of theinvention. 1

Example 3.A mixture consisting of 1350 parts of formaldehyde solution(approximately 9 mols), 930 parts of 9 .5% acetaldehyde solution(approximately 2 mols), and 358 parts of 29% sodium hydroxide solution(approximately 2.6 mols) was made in one minute. The maximum exothermicreaction temperature reached was 52 C. The mixture was then kept at atemperature of 58% C. for 11 hours. After this mately 2 mols) dissolvedin a mixture or 382 parts of 31% sodium hydroxide solution(approximately 2.8 mols) and 138 parts 0! 20% formaldehyde solution(approximately 0.9 mol) The temperature was maintained between 20 and 23C. After heating the reaction liquor to 58 C. and maintaining it at saidtemperature for 2 hours, the formaldehyde concentration determined bytitration corresponded to 0.15% formaldehyde. This solution was cooledto 25 0., neutralized to a pH of 8 with formic acid, and the specificgravity adjusted to 1.100. The polypentaerythritols time theformaldehyde concentration determined by titration with sodium bisulfitecorresponded to 0.32%.

To the abovemixture at room temperature were added in oneminute anotherbatch of the same reactants in 'the same amounts, namely,

1350 parts of 20% formaldehyde solution, 930

parts of 9.5% acetaldehyde solution, and 358 parts of 29% sodiumhydroxide solution. The maximum exothermic reaction temperature reachedwas 38 C. The mixture was then kept at a temperature of 58 C. for 12hours, after which time the formaldehyde concentration determined bytitration with sodium bisulfite corresponded to 0.35%-

To the above mixture was again added in one minute another batch ofthesame reactants in twice the previously used quantities, namely, 2700parts of 20% formaldehyde solution, 1860 parts of 9.5% acetaldehydesolution, and 716 parts of 29% sodium hydroxide solution. The maximumreaction temperature attained was 45 C. The mixture was then kept at atemperature of 58 C. for 10 hours. After this time the formaldehydeconcentration determined by titration with sodium bisulfite solutioncorresponded to 0.32%. The reaction mixture was then neutralized to a pHof 8 with formic acid. The specific gravity was 1.070 at 25 C. Thepleopentaerythritol was filtered oil, washed and dried. The filtrate wasconcentrated to a specific gravity of 1.270 at 25 C. under vacuum, andthe crystals filtered, washed well with methanol, and dried.

The yield of monopentaerythritol based on the total acetaldehyde thatwas added to the reaction mixture was 55%; the yield ofdipentaerythritol was 11.2% by fractional crystallization; and that oftripentaerythritol was 6.5%

Example 4.A mixture consisting of 1360 parts of 20% formaldehydesolution (approximately 9.1 mols) and 88 parts of 100% acetaldehyde(approximately 2 mols) was added slowly over a period of 1 hour andminutes to a solution of 272 parts of monopentaerythritol (approxiwerefiltered ofl', washed and dried. The filtrate was concentrated to aspecific gravity of 1.270, and the crystals formed were washed withmethanol and dried. Upon analysis by recrystallization, the two solidfractions were found to represent a total yield of 75.7%, based on theacetaldehyde used. This was made up of the followingindividual yieldsobtained by crystallization of the above two fractions:monopentaerythritol, 28.0; dipen'taerythritol, 39.4; andtripentaerythritoi, 8.3.

Example 5.-A mixture consisting of 627 parts of 43.1% formaldehydesolution (approximately 9 mols) and 88 parts of liquid acetaldehyde(approximately 2 mols) was added in 1 hour to 69.7 parts of 43.1%formaldehyde solution (approximately 1 mol) mixed with 437 parts of 32%sodium hydroxide solution (approximately 3.5 mols) and 272 parts ofdissolved pentaerythritol (approxi-' ma-tely 2 mols) in a completelyenclosed reaction vessel while the temperature of the mixture wasmaintained between 40 and 43 C. After heating the reaction liquor to 58C. and maintaining it at said temperature for 2 hours, the formaldehydeconcentration determined by titration corresponded to 0.35%fomialdehyde. This solution was cooled to 25 C. and processed as inExample 4.

The yield of tripentaerythritol was 29.9%; the yield ofdipentaerythritol was 38.5% and the yield of monopentaerythritol was10.2%.

Inasmuch as the foregoing description comprises preferred embodiments ofthe invention,

' it is to be understood that the invention is not limited thereto andthat modifications and variations may be made therein without departingsubstantially from the invention, which is to be limited solely by thescope of the appended claims.

Reference is made to our application Serial,

No. 739,646, filed April 5, 1947, which is a division of the presentapplication and in which is claimed subject matter disclosed but notclaimed herein.

Having thus described our invention, what we claim as new and desire tosecure by Letters Patent is:

1. The process of preparing a polypentaerythritol comprising adding toan aqueous solution containing a mixture of 1 molecular proportion ofpentaerythritoi, not less than 1.4 molecular proportions of sodiumhydroxide, and not more than 4m01ecular proportions of formaldehyde, amixture of 1 molecular proportion of acetaldehyde and sufficientformaldehyde to make the ratio of total formaldehyde to acetaldehydebetween 4% and 5 to 1.

2. The process described in claim 1, in which the ratio of sodiumhydroxide is not less than 1.7 mols and not greater than 2.0 mols to 1mol of acetaldehyde.

3. A process as defined in claim 1 in which the molecular ratio ofsodium hydroxide to acetaldehyde is not less than approximately 1.7 to 1and not greater than approximately 2.0 to 1 and the startingformaldehyde concentration is between approximately 40% andapproximately 50%.

4. A process as deflned'in claim 1 in which the temperature during theaddition of the acetaldehyde is maintained between approximately 15 C.and approximately 45 C.

5. The process of preparing a polypentaerythritol comprising adding toan aqueous solution containing a mixture of 1 molecular proportion ofpentaerythritol, not less than 1.4 molecular proportions of sodiumhydroxide, and not more than molecular proportion of formaldehyde, 9,mixture 01' 1 molecular proportion of acetaldehyde and sumcientformaldehyde to make the ratio of total formaldehyde to acetaldehydebetween 4 /2 and 5 to 1.

6. The process described in claim 5, in which the ratio of sodiumhydroxide is not less than 1.7 mols and not greater than 2.0 mols to 1mol of acetaldehyde.

'7. A process as defined in claim 5 in which the molecular ratio ofsodium hydroxide to acetalde- 8. A process as defined in claim 5 inwhich the and approximately C.

9. A process to: the production of a polypentaerythritol which comprisesadding a mixture consisting of approximately 4.5 molecular proportions0! formaldehyde and 1 molecular proportion of acetaldehyde to a reactionmixture containing approximately 1 molecular proportion ofmonopentaerythritol dissolved in an aqueous solution containingapproximately 1.4 molecular proportions of sodium hydroxide andapproximately 0.5 molecular proportion of iormaldehyde, maintaining saidreaction mixture at a temperature between approximately 15 andapproximately 45 C. during the addition of the mixture of formaldehydeand acetaldehyde, and thereafter recovering the polypentaerythritol fromthe reaction mixture.

JOHN P. REhfliNSNYDER. PHIL-1P I. BOWMAN. ROBERT H. BARTI-I.

REFERENCES CITED The following references are of record in the ille orthis patent:

UNITED STATES PATENTS Number Name Date 2,004,010 Naujoks June 4, 19352,251,236 Wyler July 29, 1941 2,325,589 Bried Aug 3, 1943

